Stabilization of chlorinated solvents with aziridines



v a... srxnmzmonnr catamaran so'LvEN WITH AZIRIDINES Edward John Watson and Donald Edward Rapp, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application February 6, 1958 Serial No. 713,525

3 Claims. (Cl. 260-6525) The present invention relates to stabilizers and is more particularly concerned with stabilization of chlorinated aliphatic hydrocarbon solvents to obtain compositions having improved acid stability. The compounds employed in accordance with the present invention may be characterized by the general formula wherein R is an aliphatic hydrocarbon radical having from 1 to 4 carbon atoms, inclusive.

In the art, vapor cleaning, i. e., vapor degreasing of metals, for example, the chlorinated hydrocarbons have been employed to the almost total exclusion of other solvents. These compounds, desirable because oftheir substantial high solvent action under the conditions of use and relative freeness from fire hazards, have major drawbacks, such as their instability under acid conditions. The acid conditions cause the degradation of the chlorinated hydrocarbon which degradation products are in many instances acids. The degradation is thought to progress in anautocatalytic manner and such degradation is catalyzed by air and light.

It is, therefore, an object of the present invention to provide a stabilizer which, when present in minor quantities in chlorinated aliphatic hydrocarbon solvents will substantially maintain the neutral condition of these solvent solutions, thereby prolonging the useful life of such solvents. Another object of the present invention is to provide a stabilizer composition which, in minor amounts, will reduce deterioration of the chlorinated hydrocarbon solvents which is catalyzed by light and air. A still further object of the present invention is to provide a stabilizer which will be recoverable with the solvent, stable at the temperatures of operation, and will not be immobilized or bound in the liquid phase by acids. These and other objects will become apparent to those skilled in the art from the following specification and claims.

It has now been found that substantial inhibition of the build-up of acid conditions in chlorinated hydrocarbon is achieved when an aziridine having the formula is added to chlorinated aliphatic hydrocarbon solvent and particularly those solvents containing the usual commercial additives such as diisopropyl amine, butylene oxide, isopropyl acetate and trimethylpentene. Good re sults are obtained when the aziridine compound, i. e.,

C=CH1 RN\ is employed in amounts of from 50 to 5000 parts by weight per million parts of chlorinated hydrocarbon.

I sdswss Pm O, H

2,878,297 a, Pa n Mer1l7a1' In accordance with the present invention, the addition of from 50 to 5000 parts of an aziridine of the type described to a chlorinated aliphatic hydrocarbon solvent composition which maycontain conventional additives will stabilize the solvent" composition under acid-produc'- ing conditions. I

Some of the compounds which are within thes'copof the present invention and may be employed in the stabilization of chlorinated hydrocarbon solvents are N-isopropylallenimine (l-isopropyl-2-methyleneaziridine), N- ethylallenimine, N-butylallenimine, N-allylallenimine and the like.

Various chlorinated aliphatic hydrocarbon solvents may be stabilized in accordance with the present invention. Thus, carbon tetrachloride, ethylene dichloride, perchloroethylene, trichloroethylene and the like may be stabilized by employment of the compounds of the present invention.

The following examples are illustrative of the present invention, but are not to be construed as limiting the same.

ACCELERATED OXIDATION TEST A chlorinated hydrocarbon solvent is heated at the reflux temperature for 48 hours in the presence of incandescent light, oxygen and iron. The formulation may not develop more than 200 parts per million (p.p.m.) of acid as HCl to be acceptable. A representative formulation employed in the test is a commercial trichloroethylene formulation containing 300 p.p.m. of butylene oxide, 2500 p.p.m. of isopropyl acetate, and 1500 p.p.m. of trimethylpentene. This formulation is hereinafter referred to as formulation A.

ACID ACCEPTANCE DETERMINATION A 20 ml. sample of a solvent formulation is refluxed for 5 minutes with an excess of alcoholic HCl; 25 ml. of water is added containing phenolphthalein. The formulation is back-titrated with standard NaOH.

Example The above tests were carried out with solvent formulation A as set forth above, and also with the formulation A plus 970 p. p. m. of N-isopropylallenimine.

The acid acceptance test was run before and after the accelerated oxidation test to show whether the aziridine additive was inactivated by exposure to oxidizing conditions.

The results are tabulated below:

Before Oxidation Test After Oxidation Test Formulation Acidity Acid .Ac- Acidity Acid Acas p. p. m. ceptance as p. p. m. ceptance H01 as percent H01 as percent N aOH NaOH A 8 0.086 over 200 0. 000 A+940 p. p. m. of N-isopropylallenimine 10 086 14 095 We claim:

1. A stabilized chlorinated aliphatic hydrocarbon solvent composition comprising from 50 to 5000 parts by weight of an aziridine compound having the formula 2. A composition as set forth in claim 1 wherein the aziridinc is 1-isopropyl-Z-methyleneaziridine.

3. A composition as set forth in claim 1 wherein the chlorinated aliphatic hydrocarbon is trichlorocthylene.

References Cited in the tile of this patent 

1. A STABILIZED CHLORINATED ALIPHATIC HYDROCARBON SOLVENT COMPOSITION FROM 50 TO 5000 PARTS BY WEIGHT OF AN AZIRIDINE COMPOUND HAVING THE FORMULA 